I have finished all of the two and three player challenges, but after that it really gets hard to set up a room where everyone will participate. My gamertag is SonicBlackzero and if you would like to help me please reply ASAP and I will set up a match.

I have a ton of challenges to complete still so I will help with some. Maybe now right at this moment though.

You can always look into having a Burnout Bombing Run, just talk to a mod, or other interested members  about getting it organized.  Check out this thread for getting the word out.

Oh, dude I'd be willing to help. I need four player challenges too (and three player, and two player, and every other player). My GT is StarFoxA, just send me a message and we can set up a time.
 
I'll see if my friend Metroid545 is willing to help too.